The Author(s) 2018. This article is published with open access at www.chitkara.edu.in/publications.

ABSTRACT

This work presents the development of an analysis of the potential radiological risk generated by alpha particles emitted by radon-222, content in a spring water, for the population that usually swims in the place and for the people who live near this spring. This spring is located in the state of Puebla. Several measurements in the water of this place by researchers from IF-UNAM showed that it contains an average radon concentration level of 70 Bq/m3. To evaluate this radiological risk, it has been developed a computational simulation to know the area and the height where the alpha particles deposit their energy to the medium, as well as the amount of energy that they transfer. This simulation was developed in the Geant4 scientific software and the calculations were executed in the supercomputer of the Laboratorio Nacional de Supercomputo del Sureste de Mexico of the BUAP. The results show that the energy deposit occurs within the superficial limits of the spring, between 7 and 8 meters high. This deposited is not only by the alpha particles, but also by the secondary particles that are generated by the interaction of alpha particles with the environment. Based on these results, it is confirmed that there is no radiological risk by energy deposit by alpha particles for the people.

INTRODUCTION

The concentration of radon-222 in the air inside homes and work spaces [1] is a matter of public safety [2], because according to different international organizations such as the United States Environmental Protection Agency (US-EPA) and The World Health Organization (OMS), radon is the second cause of lung cancer (only after snuff). In the United States, it is estimated that around 15,000 to 22,000 people die each year for an illness caused by the radon gas. For this reason, it is extremely important to quantify their levels and mitigate them when their concentration is greater than the limits recommended by the different organizations dedicated to radiation protection. However, the situation it gets complicated if is analyze the possibility that the radon that comes from the subsoil is concentrated in the spring water and wells that are used by people for different purposes. [1]. Suffice it to say that the volume of groundwater is much greater with respect to the mass of water that is retained in the lakes and that found in the surface rivers. Therefore, radon in the water would imply a double risk for the population. On the one hand, there is the fact that radon that is emitted by water can affect the lungs of people who inhale it and, on the other hand, there is a risk that radon will enter the stomach of those people who ingest it, generating the possibility of produce stomach cancer; although the risk of contract stomach cancer from ingest water with radon is lower with respect to the risk of contract lung cancer by inhaling radon (only 11% of the population that gets cancer from radon will develop it in the stomach compared to 89% will develop in the lungs) [3]. This means that it is not enough to quantify radon in homes and work spaces, it is also important to measure their concentration levels in all the springs and wells that exist around the world before being used to irrigate crops, such as water for human consumption or for recreational activities. Table 1 presents the concentration value of radon contained in water for human consumption recommended by the US-EPA.

The quantification of radon-222 concentration levels must not only be carried out in people’s homes and workspaces, but also in the water of spring and wells used for different purposes. The risk of a concentration level greater than that recommended by the different organisms dedicated to radiological protection is greater, because this gas can not only enter and make the lungs sick of people who inhale it, but also the stomach of those people who ingested it. In addition, radiological protection mechanisms should not only focus on measuring levels of concentration in water, but also on the development of computational simulations that allow analyzing the range of gas expansion when it is emitted by water, or the zones where radiation by alpha particles interacts and deposits its energy with the air. To carry out this type of simulations, it is possible to use the multiple softwares that exist to simulate the interaction of radiation with matter, such as the Geant4 software. This work simulated the emission of alpha particles by radon-222 contained in the water of a spring, whose dimensions are 15 × 10 × 5 meters, and whose radon concentration is 70 Bq/L, with the purpose of studying the zones where the radiation deposits its energy and to assess the radiological risk to which the people who live around the spring or who swim in this place are subjected. The results showed that the radiation deposits its energy at a height of 7.5 meters in height, from where the particles are emitted, and in an area that is within the surface limits of the spring. Therefore, a radiological risk generated by radiation of alpha particles in this place is ruled out. However, it is necessary to make an additional model that contemplates the expansion of radon gas, in order to have a better certainty of the low radiological risk represented by radon in the water of this spring for people.